function xc = get_xc(X,mu)
if exist('bsxfun','builtin')==5
    xc = bsxfun(@minus,X,mu);
else
    %function bsxfun is not available (older Matlab)
    xc = X;
    for iii=1:size(xc,2), xc(:,iii) = xc(:,iii)-mu(iii); end
end
